1. Technical Field
The invention relates to axle suspension systems for wheeled vehicles, and in particular to beam-type axle suspension systems for wheeled vehicles. More particularly, the invention is directed to a beam-type axle suspension system for tractor-trailers in which each beam tapers from a narrower width at its end that is pivotally attached to the trailer frame without special mounting accessories and utilizing a reduced size bushing.
2. Background art
The use of air-ride beam-type axle suspension systems and air brakes has become very popular in the heavy-duty truck and tractor-trailer industry. Although such suspensions can be found in wide and varying structural forms, in general their structure is similar in that each system typically includes a pair of longitudinally extending beams. Each beam is located adjacent to and below a respective one of a pair of spaced-apart longitudinally extending frame rails which depend from the trailer. More specifically, each beam is pivotally connected at one of its ends to a hanger which is attached to and depends from a respective one of the frame rails. An axle extends transversely between and is mounted in openings formed in the beams generally adjacent to the end of the beam opposite from the pivotal connection end. The opposite end of each beam also is connected to a bellows air spring or its equivalent which in turn is connected to a respective one of the trailer rails. A brake assembly and shock absorber typically also are mounted on each of the beams. The beam may extend rearwardly or frontwardly relative to the front end of the tractor-trailer, thus defining a trailing arm or leading arm beam suspension system, respectively.
Also, it is well-known that air-ride beam-type axle suspension systems generally require a substantial bushing at the pivotal attachment point of each beam to the trailer frame rails for satisfactory reaction to static loads, roll moments and braking forces. This bushing requirement results in a wide hanger bracket depending from each of the trailer frame rails, which requires shims and other accessories for proper anchoring to the frame rails. This additional mounting equipment is a penalty when compared to prior art narrow leaf spring designs which generally fit within the confines of the trailer frame rails and therefore can be mounted thereto without additional assemblies.
Moreover, the weight of beam-type air suspension systems generally is greater than leaf spring suspension systems.
The present invention solves the problem of complicated mounting of the beams to the trailer rails and overall excessive weight of the system. These problems have been solved in the present invention by attachment of the pivotal end of the beam to a frame bracket which fits within the confines of a conventional trailer frame rail and is relatively easily anchored thereto, which in turn also enables use of a smaller pivot bushing. Moreover, the present invention optimizes the weight of the beam by removing material in its lower stress portions adjacent to the pivotal attachment end.